Our main objective is to prepare inhibitors of protein biosynthesis and to study the mechanisms of peptide bond formation at the ribosomal level. We have recently prepared a carbocyclic puromycin analog which can be used as a model for these studies. By preparing other analogs of this type we can make a wide variety of structural modifications for use in mapping ribosomal binding regions. We plan to find different binding requirement among ribosomes from different sources which will enable us to prepare selective inhibitors of protein synthesis.